Air-cooled burner for furnaces



May 9, 1950 F. H. Lor-Tus AIR-COOLED BURNER FOR FURNACES llll l Il. Il

lllllll/l flllllllll//llllI/l/ l INVENTOR.

Fred H. Loftus M MM www Filed Jan. 29, 1947 May 9, 1950 F. H. LQFTUSAIR-COOLED BURNER FOR FURNACES Filed Jan. 29, 1947 2v Sheets-Sheet 2INVENTOR. Fred H. Loftus Patented May 9, 1950 UNITED STATES TENT FFICEAIR-COOLED BURNER FOR FURNACES Fred H. Loftus, Mount Lebanon, Pa.

Application January 29, 1947, Serial No. 725,009

3 Claims. (Cl. 158-7) This invention relates to the construction ofburners, particularly to burners for the combustion of fluid fuel inindustrial furnaces. The burner of this invention is more particularly,though not exclusively, adapted for firing furnaces used in the heattreatment and/or anhealing of metal products, such, for example, assheet steel which is ordinarily treated in boxtype or cover-typefurnaces.

A burner of the sort to which this invention is especially directedcomprises an elongate duct having a plurality of outlets for the releaseof jets of fuel at points spaced apart longitudinally on the burnerbody.

The iiuid fuel used with burners of the type in mind is ahydrocarbonaceous gaseous or vaporous fuel, which, under the effect ofthe heat to which the burner is subjected to in service, deposits carbonupon the surfaces of the burner body, and tends to plug the orifices orpassages through which the fuel flows. With this circumstance in mind,it will be understood that this invention consists in certain new anduseful improvements in burner construction, whereby the fuel-conductingportions of the burner body are screened from extreme furnacetemperatures. Additionally, the burner structure is such that theportion or portions thereof which tend to become fouled withaccumulations of carbon may be readily removed from the '1 burnerstructure, and a spare portion substituted. In consequence, it becomespossible to maintain the burner, and the furnace in which it ls used, insubstantially continuous operation; that is to say, it is no longernecessary to withhold the furnace from service in order to permit theremoval of accumulated carbon from the `burner or burners of thefurnace.

The invention will be understood upon reference to the accompanyingdrawing, in which:

Fig. 1 is a fragmentary view showing a burner embodying the invention inside elevation. By way of example, this view shows the burner inposition of service within the burner chamber of a box-type annealingfurnace, the refractory walls of the chamber in the furnace structurebeing indicated fragmentarily in vertical section;

Fig. 2 is a fragmentary view of the burner structure as seen in planfrom above;

Fig. 3 is a fragmentary sectional view of the burner installation tolarger scale, as seen on the plane III-III of Fig. 1; and

Fig. 4 is a fragmentary view of the burner, partly in longitudinalvertical section and partly in side elevation. This view shows theburner on larger scale than Figs. 1 and 2, but on smaller scale thanFig. 3.

Referring to the drawings the burner comprises an elongate fuel duct 2and an air duct 3. The air duct is positioned immediately above the fuelduct, and is substantially coextensive in length therewith. In servicethe burner is usually arranged within an elongate tunnel-like chamber,such as the chamber 50 within refractoryv body 5 of the furnacefragmentarily indicated in Figs. 1 and 3. Angle members 4 are welded tothe fuel duct, providing feet upon which the burner structure issupported upon the floor of the chamber 50. The roof of the chamber 50is provided with a series of ports 6 through which the burner is adaptedto deliver burning jets of fuel and air into the combustion chamber orzone located in the furnace above the roof or top wall 5 of the burnerchamber 50.

The fuel duct 2 of the burner is advantageously formed of an inner tube'I telescopically assembled Within and encased by an outer tube 8; theinner tube I is substantially smaller in diameter than the tube 8 and isprovided with lugs 9 which support the inner tube in concentric relationwith respect to the outer tube 8, with a substantial thermal insulatingspace I0 provided between the walls of the inner and outer tubes. Theburner structure at one end (the right-hand end, Fig. 1) extends beyondthe walls of the furnace structure, where an inlet is provided fordelivering fuel to the inner tube of the fuel duct 2, and an inlet fordelivery of combustion air to the air duct 3.

More particularly, the outer tube of the fuel duct is equipped with aflange I I through which the inner tube l extends to a threadedterminal, by means of which connection is made to a fuel supply pipe I2.The inner tube 'I carries a flange I3. The flanges II and I3 are boltedtogether, detachably securing the tubes 1 and B in assembly.

The air duct 3 is positioned immediately abov the fuel duct 2, with theaxes of the two ducts located in the same vertical plane. The air ductis of substantially larger diameter than the fuel duct, and in this caserests upon the top of the fuel duct. An inlet for air is provided at theend of the burner where the fuel inlet is located. The air inlet isformed by a vertical pipe section I4 welded upon the end 0f air duct 3,and the pipe section I4 is flanged at its upper end, Whereby it may bedetachably bolted to the flanged end of a pipe I5 which supplies thecombustion air to the burner. Preferably the inlet pipe section I4extends downward below the air duct 3, and is ported for the passage ofthe fuel duct 2 through it, the lower end of the section I4 thus formingan additional supporting member for the burner structure. Blankingplates or bulkheads I6 are welded across the bore of pipe section I4above and below the fuel duct, as shown in Fig. 4.

At points spaced apart longitudinally of the fuel duct radiallyextending jet pipes I'I are provided. These jet pipes are welded inhermetic seams I8 to the outer tube 8 of the fuel duct, and in theburner shown ithegjetipipes rise in a vertical line, projecting upwardlythrough the air duct 3. The wall of the 'airduct'is orificcd, as at 20and 2I, to permit -the passage through of the jet pipes. The jet pipesare united to the wall of the air duct by continuous hermetic welds inthe upper orices 20, and, if desired, by intermittent tack welds'in`the-lower -orificesiZI. .Removable -nozzle sleeves I9 (Fig. 3) arepositioned upon the projecting upper ends of the jet pipes. -As shown,these jetpipes 'are sevverally aligned with `the ports :6 kin the topwall oftheburner chamber D. Passages-Rand 22 are fformed in the walls'ofthe innereand outer tubes 'J1 and 8, respectively, of theffuel duct,and through 'such passages 'communication is established beltween'thefuel-deliveringttube 'I and the jet-.pipes severally. :'Eachofthe'passages 23 inithe inner ftube comprises a relatively small orifice,whose fsize is determined "to give the desired ow lvof "fuel into -the4associate jet pipe, v.while .the Acorresponding passage 22 in :theouter tube Il is' comparatively large. The "function of "the pas- IsageA22 is primarily to provide .unrestrictedzpas- 'sage of the fueljetdelivered'by the associate `orifice 23 into the jet pipe above.

The jets of fuel are directed upwardly from .the `jet lpipes and nozzles.through .the ports 6, and air is released from the air duct V3'tofurnish combustion air 4for thefuel jets projected into the furnacechamber or combustion zones above the 'top .wall of theburner chamber..This combustion air is released by thefuel duct at .dis-

tributed points inthe extent of the iburnenand advantageously theainreleaseis effected by forming the orifices .2l in the wall ofthe air;duct 'larger than the bodies 4'0f the jetpipes, as :may be understoodupon lreference to Fig. 3. Around each of the jet pipes, therefore, aclearance is provided, through which Lair 'is delivered Yinto ythe'burner chamber 5D, and Vfrom this chamber the air is aspirated by theaction fof A.the Vfuel jets "flowing upwardly through .ports :6. A com-`bustiblemixture of^fuel and airis thus .delivered ,upwardlyfrom each ofthe'ports 6.

[As noted in the introduction to this speciication a problemin thevoperation'o'f 'burners fir- ,ing fluid 4hydrocarbon fuels'hasiheretofore been r.caused by the deposition'of carbon Vupon the bodyand in the passages of the burner, thiscleposition/of carbon *beingcreated-by theheat to vwhich the lbody of the burner lis subjected inservice. jln'Fig. 3 the arrows-indicate the directions .in whichthegreatest quantity'of lheatllows or'radifates into the chamber. Itwill'be understood, Yof course, that when the furnace is Vin fserviceall Vof 'the refractory 'rwalls 5 -which `.define the burner chamber 50heat up, but theA highest temperatures are developed in the upper wallportions `of the chamber, and greatest heat is radiated vdownwardlyinthedirectionof the ai-rows.

EIf the :portion :of any .burner carrying a hydrocarbon fuel isprevented from becoming excessively hot, the problem in question ispractically solved. The structure of the burner of this invention isparticularly effective to this end.

The inner tube 'I of the fuel duct is the more critical element of theburner structure, since it is this tube which carries the fuel, and itis this tube which includes the relatively small ori- .ces (23) whichtend to become clogged with accumulations of carbon. It will be notedthat the tube I is housed or encased within the outer `tube 8, and thusreceives primary protection against excessive heat. Additionally, thedead space IIl, while filled with the gaseous fuel, provides a thermalscreen for the fuel-conducting tube The position and the relativelylarge diameter of the air duct 3 are important, since the -air ductshades the fuel duct from the most acute heat radiated in .lthedirections of the arrows. Furthermore, the duct 3, conningafcontinuouslyflowing stream of relatively cool fair, exerts a `cooling as well as ashading" effect uponthe fuel duct. Also, it is importantto .note

clean the relatively small oriiices23of the burner,

irrespective of the degree to which the deposition of carbon isinhibited. Hitherto, burners of ythe class herein under considerationhad to-beremoved from the furnace to permit cleaning, or in some casesthe furnace has been removedffrom service and the burner cleaned, afterthe furnace has been cooled down -to the point -where vworkmen couldenter.

In the burner structure of this invention, such furnace lshutdowns Iareavoided. It is merely necessary to :remove the bolts which secure theflanges II .and I3 -together, vdisconnect the coupling |20 in theffuelsupply line, and then Withdraw ythe innergtube uTI of the fuel duct fromthe burner structure. 4A spare inner tube I is then quickly assembled1in place of the inner tube removed, and furnace operation can proceedwithout undueinterruption. The removed inner tube can be cleaned .atleisure, and held in readinessas aspare.

Theappended claimsdeiine :the invention with the understanding thatmanyvariations orzmodifications maybe made in the structure describedwithout departing from the spirit of the invention.

I claim:

1. A burner structure comprisingan elongate fuel duct in the form-of anouter cylindrical 'tube having an inner cylindrical tube removablypositioned therein, an inlet vfor vthe introduction @of fuel to saidinner tube, an elongate cylindrical air duct of greater ,diameter thanthe fuel duct, said air duct being superimposed upon-said -fuel duct inposition to screen the fuel duct from heat radiated downwardly frompoints above the burner structure, an inlet for the introduction of airto said air duct, and ya plurality of jetpipes extending from said fuelduct `at spaced-.apart points longitudinally Athereof vand "projectingtransversely'through said air'duct, the vwalls of said inner and .outertubes of the fuelductincluding passages for the flow of fuel from saidinner tube into said jet pipes severally, and the wall of said air ductincluding in its bottom wall portion a plurality of outlet passagesspaced apart longitudinally of the air duct for the delivery of air overthe external wall of the outer tube of said fuel duct,

2. A burner structure comprising an elongate fuel duct in the form of anouter cylindrical tube having an inner cylindrical tube removablypositioned therein, an inlet for the introduction of fuel to said innertube, an elongate cylindrical air duct of greater diameter than the fuelduct, said air duct being superimposed upon said fuel duct in positionto screen the fuel duct from heat radiated downwardly from points abovethe burner structure, an inlet for the introduction of air to said airduct, and a plurality of jet pipes extending from said fuel duct atspaced apart points longitudinally thereof and projecting transverselythrough said air duct, the walls of said inner and outer tubes of thefuel duct including passages for the flow of fuel from said inner tubeinto said jet pipes severally, and the wall of said air duct includingin its bottom wall portion at the points where said jet pipes projecttherethrough passages for the delivery of air over the external Wall ofthe outer tube of said fuel duct.

3. In combination, a tunnel-like chamber provided with openings at itstop for upwardly directed jets of burning fuel, a burner structuremounted to extend longitudinally of said chamber, said burner structurecomprising an elongate fuel duct in the form of an outer cylindricaltube having an inner cylindrical tube removably positioned therein, aninlet for the introduction of fuel to said inner tube, an elongatecylindrical air duct of greater diameter than the fuel duct, said airduct being superimposed upon said fuel duct in position to screen thefuel duct from heat radiated downwardly through said openings and fromthe upper wall portions of said chamber, an inlet for the introductionof air to said air duct, and a plurality of jet pipes extending fromsaid fuel duct at spaced-apart points longitudinally thereof andprojecting transversely through said air duct in line with said openingsat the top of said burner chamber, the Walls of said inner and outertubes of the fuel duct including passages for the iiow of fuel from saidinner tube into said jet pipes severally, and the wall of said air ductincluding in its bottom wall portion a plurality of outlet passagesspaced apart longitudinally of the air duct for the delivery of air overthe external wall of the outer tube of said fuel duct.

FRED H. LOFIUS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 322,791 Chess July 21. 1885328,914 Ashcroft Oct. 27, 1885 1,758,828 Fisher et al. May 13, 19302,130,165 Warren Sept. 13, 1938

